The present invention relates to a steering lock that locks a steering shaft with a lock bar.
Electronic steering locks for use in an automobile have been proposed in recent years. Such an electronic steering lock includes an electronic control unit (ECU) and a motor. The ECU controls the motor to produce torque used to move a lock bar so that the lock bar engages with or disengages from a steering shaft. The lock bar locks the steering shaft when engaged with the steering shaft and unlocks the steering shaft when disengaged from the steering shaft.
In an electronic steering lock, electric noise may cause the ECU to erroneously function and drive the motor in an unintended manner. Therefore, electronic steering locks are configured so that they do not lock the steering shaft when the vehicle is traveling. For example, Japanese Laid-Open Patent Publication No. 2003-063354 describes a steering lock provided with a power line, which includes a relay and a plurality of field effect transistors (FETs), for supplying the motor with power. The FETs are series-connected to the relay, which is connected to the motor. In this steering lock, the relay and the FETs must all be activated to drive the motor. This prevents the steering lock from locking the steering shaft when the vehicle is traveling even if electric noise causes the ECU to function erroneously.
Nevertheless, with the structure in which the FETs are series-connected to the relay, there still is a possibility of the motor being driven in an erroneous manner.